In recent years, the cost increases associated with rising fuel prices and introduction of environmental regulations have led to a need for tires with excellent fuel economy in the transportation business. In order to improve fuel economy, Patent Literatures 1 to 3 for example propose methods in which rubber to be used in a silica-containing composition is addition reacted with a specific polar group so that the rubber has an affinity for silica. Although the methods enhance the reaction efficiency between silica and rubber (polymer) to improve fuel economy, the methods tend to increase Mooney viscosity so that processability can be deteriorated. Moreover, there has been a recent demand for more improved fuel economy.
Furthermore, among automobile tires, truck or bus tires need to have particularly excellent abrasion resistance and rubber strength. However, these properties and fuel economy have a tradeoff relationship. Thus, methods are needed to achieve balanced improvements in processability, fuel economy, rubber strength, and abrasion resistance.